New banana cultivars will help in Panama TR4 fight

American Professor Randy Ploetz, says resistant cultivars are the best way forward for Australian banana growers facing a future with Panama Tropical Race 4 disease.

Speaking as one of the international keynote speakers at Congress, Professor Ploetz said Cavendish banana production would never be the same in Australia again.

His predictions came prior to the news of the second TR4 detection on a Tully farm in July.

In giving an update on international research on the disease’s management, he said there were some realities Australian growers would need to come to terms with.

“Whenever anyone considers managing this, you need to consider if it is economical,” Professor Ploetz said.

“Can you continue growing bananas the way you were?”

Professor Ploetz listed off several of the management techniques tried for TR4 such as fumigants, biological controls, flooding and suppressive soils but said each was limited in its own way.

“The ones that have done field studies with biological controls show, that you don’t get sustainable management. It’s in two or three years later you get tremendous disease,” he said.

“To me, history has shown clearly that the only sustainable way to manage this problem is with resistant cultivars.

“It’s going to be really challenging to come up with a Cavendish-like cultivar through conventional measures that would resist this disease and would have all the other characteristics you would want in a Cavendish cultivar.

“Consider all options before you say, no, I can’t manage this disease.”

He spoke of somaclonal variants, plants produced through micropropagation, mutants that are genetically similar to the original plant, but said they generally have longer production cycles and lower yields, plus some have a problem with splayed fingers.

Front row observer

Professor Ploetz has watched the disturbing development and spread of banana diseases throughout the globe in the past 30 years.

He said the original strain of Panama disease (race one) virtually wiped out the most prolific banana variety, Gros Michel, until the Cavendish was widely adopted due to its resistance to the strain.

“More recently, and more scary to me, is the popping up of TR4 around the world,” Professor Ploetz said.

“This problem is really serious. So the fact that you are taking it really serious here in northern Queensland and you’ve come to grips with it in the Northern Territory, is good because this is probably the most serious disease for bananas.

“I work on a lot of different diseases in bananas but this one is really pernicious.”

One of the aspects to TR4 which is difficult for many to come to grips with is its longevity in a paddock.

TR4 can remain within a block for a decades.

“Once you have a field infested with this pathogen, whether it’s race one or TR4, it’s in that field for a very long time,” Professor Ploetz said.

“I can’t overstate the importance of that. Once you’ve got an infested field, you can’t go back to that field with that same cultivar and expect to produce that cultivar.”

He said he thought one of the main reasons the pathogen stays on for so long is that certain weeds can act as hosts, thus he encouraged those undertaking research into TR4 weed hosts.

“It’s a no-brainer that if you establish new plantings in an area and you’ve got this disease, you do not want to use traditional suckers so tissue culture plantlets are free of this pathogen,” he said.

Practice changes

While he said some researchers have spoken and written on the effectiveness of healthy, clean soil acting as a suppressor to TR4, he said it was the weeds that helped the pathogen to linger, and said tissue culture plantlets were the way to go for new plantations.

Banana growers may need to re-consider how they irrigate as well, with the pathogen easily held in surface water sources.

The disease was rapidly spread in China by pumping from infected water sources, essentially inoculating entire plantations.

“If you have the potential to use bore hole water when you irrigate, I highly recommend that,” he said.

When it comes to biosecurity, Professor Ploetz said growers should seek out the best sanitary products available to wash down machinery, tools and to use in footbaths.

He said footbath solutions are very effective provided no organic material or large amounts of soil sit within them.

Biosecurity vigilance

Professor Ploetz commended the Queensland banana industry on their vigilance to date.

The question for many in north Queensland currently is: How widely spread is TR4?

“The good thing there is people are on red alert. They are aware of how difficult this problem is to manage and they are aware that you’re not going to come on my plantation unless you have clean boots, and that we are going to hose you down, and so forth,” he said.

He encouraged Biosecurity Queensland to keep up its visual inspections of banana plantations, and also floated the idea of using aerial examination to assist.

Australian Banana Growers’ Council R&D manager, Dr Rosie Godwin, spent a week in June with Professor Ploetz and French banana researcher, Dr Frédéric Bakry, travelling north Queensland banana production areas, meeting local scientists and giving the visiting researchers an insight into Australian banana production and biosecurity practices.

“The banana industry is fortunate to have significant investment in fundamental and applied research projects which are targeted at finding solutions to the many pest and disease threats the industry faces,” Dr Godwin said.

*This article was originally published in the Good Fruit and Vegetables Magazine.